The invention relates to stereoblock polymers containing at least one saturated or unsaturated polyolefin type sequence, or a polydiene, which may be linear or branched, comprising at least one succinimide ring substituted on the nitrogen atom by a reactive group, said ring being supported either by the main chain, or by a side chain, and containing at least one sequence with a variety of natures, other than a polyolefin. The polymers used to prepare the polymers of the invention are of the thermoplastic elastomeric type and are bi-, tri- or multi-sequenced.
The invention also relates to mixtures of a plurality of graft stereoblock polymers as defined above and to mixtures of such graft stereoblock polymers with other polymers, such as polyamide, polyether, polyolefin or polyurethane type polymers. It is possible to add substances to the mixture to obtain properties which are appropriate for the desired applications. European patent EP-A2-0 295 706 mentions those different substances and should be considered to be incorporated by reference. By way of example, the mixture of polymers can contain stabilisers, such as antioxidants or ultraviolet absorbers, lubricants, colorants, flame retarders, nucleation agents, paraffinic or naphthenic oil type plasticizers, reinforcing fibres which increase the value of the Young""s modulus and the break strength, such as glass fibres, carbon fibres, boron fibres, or ceramic fibres, or organic or inorganic fillers, such as titanium dioxide or zinc oxide.
Regarding the current state of the art, the article in the xe2x80x9cJournal of Applied Polymer Sciencexe2x80x9d, 1997, vol. 63, no3, pages 275-281 shows that adding a small quantity of a polyolefin grafted by a maleic anhydride in a PE-BD (low density polyethylene)/PP(polypropylene)) mixture improves the compatibility between those two polymers, which are initially non miscible. A further method for improving compatibility consists in introducing a copolymer between the two incompatible polymer phases, to improve the mechanical properties of the mixture obtained. In a further article in the xe2x80x9cJournal of Applied Polymer Sciencexe2x80x9d, 1997, vol. 65, no2, pages 2457-2469, a PBT/EVA, [poly(butylene-terephthalate)/(ethylene-vinyl acetate copolymer)] graft copolymer renders PE/PBT [polyethylene/poly(butylene-terephthalate) mixtures compatible. Increasing the number of vinyl acetate units in an EVA copolymer increases the compatibility with PE. Adding a copolymer containing elements which are miscible with the components of the mixture changes the morphology of the system. The PBT particle size is reduced, which encourages compatibility between the two phases.
The present invention relates to modified polymers containing a reactive group which is grafted onto a polyolefin or a polydiene, to improve the dispersion and adhesive properties. They are graft stereoblock polymers which have improved adhesive properties compared with non grafted stereoblock polymers. In particular, they can be used as adhesives, compatibilisers or resiliency agents.
The graft stereoblock polyolefin or polydiene type polymers of the invention have reactive groups which enable them to be used for the production of mixtures of polymers. They contain at least one succinimide ring substituted on the nitrogen atom by a reactive group, said ring being supported either by the main chain, or by a side chain, resulting from the reaction of at least one stereoblock polymer with a compound comprising at least one maleimide ring substituted on the nitrogen atom by a reactive group with formula xe2x80x94R(xe2x80x94X)xe2x96xa1, where xe2x80x94X represents a reactive group, n is a number which is greater than or equal to 1 and xe2x80x94R is a residue containing at least one carbon atom; also included are polymers which derive therefrom by reaction with at least one polyepoxide containing at least two epoxy groups in its molecule. The compound comprising a maleimide ring is represented by formula (I) below: 
Reactive group xe2x80x94X is normally selected from a hydroxyl group, a carboxyl group, a carboxamide group, a carboxylic acid halide group, a thiol group, a thiocarboxyl group, an amino group, a halogen, an epoxy group, or an esterified carboxyl group, the ester portion of which comprises a reactive group. When a plurality of xe2x80x94X groups are present, they can be identical or different.
This reactive group is usually either selected from groups which can react with epoxy functions by oxirane ring opening, in the case of a residue containing at least one polyepoxide, or selected from the carboxyl group, the carboxamide group and acid halide groups, for example a carboxylic acid chloride. The preferred group is the carboxyl group.
The xe2x80x94Rxe2x80x94 group is normally selected from substituted or non substituted, saturated or unsaturated aliphatic hydrocarbon groups, and substituted or non substituted aromatic groups. In general, non substituted groups are preferred, usually groups comprising at least one aromatic nucleus. Examples of frequently used groups are benzene groups bonded ortho-, meta- or para- to the nitrogen atom and to the reactive group xe2x80x94X. Usually, the para- or meta- form is used.
The polyepoxide used in the present invention containing at least two epoxy groups in its molecule, is usually selected from the group formed by aliphatic polyepoxides, cycloaliphatic polyepoxides and aromatic polyepoxides. Examples of compounds which are usually used are the diglycidylether of bis-phenol-A or bis-phenol-F, triglycidylether-isocyanurate and/or triglycidylether-cyanurate and/or triglycidyl-isocyanurate and/or triglycidyl-cyanurate or novolac epoxides, or mixtures of at least two of these compounds. The epoxy compounds comprising at least two epoxy groups cited in United States patent U.S. Pat. No. 4,921,047 are also suitable in the present invention. The teaching of that patent should hereby be considered to have been incorporated by reference.
The sequence for grafting the graft stereoblock polymers is a polyisoprene, polybutadiene, poly(ethylene-butylene), poly(ethylene-propylene) or other polyolefins and is optionally grafted via polyisoprene or polybutadiene links.
The sequences other than the polyolefin or polydiene type contained in the stereoblock polymers of the present invention are of a variety of natures. They are obtained by conventional polymerisation routes which are well known to the skilled personxe2x80x94by addition, by condensation, or by ring opening. Non limiting examples are polystyrenes, polyvinyls and their derivatives, such as polyvinyl halides, polyvinylacetals, polyvinylacetates, polyvinyl alcohols, polyvinyl esters or polyvinyl ethers, polysulfides, including polyphenylene sulfides, polyacrylonitriles, polyethers, including polyalkylene oxides and polyphenyl ethers, polyesters, polyacrylic acids, polyamides, including polyacrylamides, polyimides, including polyether imides, polyamide imides, polyurethanes, polyureas, polyurethane ureas, polyester urethanes, polyether urethanes, polysulfones, polyketones, aromatic polyesters, including polycarbonates, polyethylene glycols, polyacrylates and polymethacrylates, polysiloxanes, polyether sulfones, polyether ketones, organometallic polymers, such as silicones, and polymers containing phosphorous or other heteroatoms.
The graft stereoblock polymers of the present invention are prepared using different methods. A first method consists of bringing a stereoblock polymer containing at least one sequence of a variety of natures and at least one polyolefin or polydiene type sequence into contact in the molten state with at least one compound comprising a maleimide ring substituted on the nitrogen atom by a reactive group, in a kneader or extruder, to produce a graft stereoblock polymer.
Bringing a stereoblock polymer containing at least one sequence of a variety of natures and at least one polyolefin or polydiene type sequence in the molten state into contact with at least one compound comprising a maleimide ring substituted on the nitrogen atom by a reactive group and at least one compound containing at least two epoxy groups in its molecule in a kneader or extruder can also produce graft stereoblock polymers.
This type or preparation can be carried out with or without a radical initiator. Examples of radical initiators are peroxides. Within the context of the present invention, it is preferable to work without a radical initiator. This possibility of forming polymers containing a succinimide ring substituted on the nitrogen atom by a reactive group without a radical initiator, said ring being supported either by the main chain or by the side chain, is a distinct advantage of the present invention, which avoids risks of cleavage and cross-linking of the polymer. The reaction temperature is normally in the range from the melting temperature of the polymer to about 300xc2x0 C. Usually, this temperature is about 200xc2x0 C. to about 260xc2x0 C. The reaction time is relatively short and normally does not exceed 10 minutes. Normally, an extrusion-reaction system is preferably used, with very good results.
A further method for preparing the graft stereoblock polymers of the present invention consists in a step a) for bringing a stereoblock polymer containing at least one sequence of a variety of natures and at least one polyolefin or polydiene type sequence into contact in the molten state with at least one compound comprising a maleimide ring substituted on the nitrogen atom by a reactive group in a kneader or in an extruder, then in a step b), introducing at least one compound containing at least two epoxy groups in its molecule into the kneader or extruder. This preparation can be carried out with or without using a radical initiator. Examples of radical initiators are peroxides. Within the context of the present invention, it is preferable to work without a radical initiator. This possibility of forming polymers containing a succinimide ring substituted on the nitrogen atom by a reactive group without a radical initiator, said ring being supported either by the main chain or by the side chain, is a distinct advantage of the present invention, avoids risks of cleavage and cross-linking of the polymer. The reaction temperature in step a), as in step b), is normally in the range from the melting temperature of the polyolefin to about 300xc2x0 C. Usually, this temperature is about 200xc2x0 C. to about 260xc2x0 C. The reaction time is relatively short and normally does not exceed 10 minutes for each of the steps. Normally, an extrusion-reaction system is preferably used, with very good results. The temperature is normally identical in both steps.
The present invention also relates to mixtures comprising at least two polymers which are different from each other, at least one of which is a graft stereoblock polymer comprising at least one polyolefin or polydiene type sequence with at least one succinimide ring substituted on the nitrogen atom by a reactive group and other sequences of a variety of natures, as described above, or a polymer prepared using one of the preparation methods described above. The reactive function present in the graft stereoblock polymer improves the formation of said mixtures. These mixtures are used for the production of adhesives, as the mixtures have better adhesive properties than those of mixtures of polymers containing non grafted stereoblock polymers. They are also used for the production of products obtained by different transformation processes such as extrusion, injection or calendering and other transformation processes, or for the production of multilayered materials, adhesives or resiliency agents.
The mechanical properties change with the proportion of the different sequences in the graft stereoblock polymer. If the proportion of graft polyolefin is low and the other sequences represent polymers with rigid mechanical properties, the graft stereoblock polymer is shock resistant.
The entire disclosure of all applications, patents and publications, cited above and below, and of corresponding French application 98/07401, filed Jun. 10, 1998, are hereby incorporated by reference.
The following examples illustrate the invention without limiting its scope.